Ultra wideband-type technology is distinguished from narrowband and spread spectrum technologies in the sense that the bandwidth of the signal of ultra wideband type is typically between about 25% and about 100% of the central frequency or else greater than 1.5 GHz. Moreover, instead of transmitting a continuous carrier modulated with information or with information combined with a spreading code, which determines the bandwidth of the signal, ultra wideband technology involves the transmission of a series of very narrow pulses. For example, these pulses may take the form of a single cycle, or monocycle, having a pulse width of less than 1 ns. These pulses that are extremely short in the time domain, when transformed into the frequency domain produce the ultra wideband spectrum that is characteristic of UWB technology.
In UWB technology, the information conveyed on the signal may be coded for example by a digital pulse interval modulation (DPIM modulation). With such a modulation, the value of the spacing between two consecutive pulses of the pulse train codes the value of the information. Furthermore, each of the possible spacings is an integer multiple of a base duration.
The decoding of the pulse train comprises in particular the detecting of the positions of the various pulses so as to determine the values of the durations separating them. It is known that the amplitude of a signal decreases in the case of a transmission while the distance between the emitter and the receiver is increasing.
An approach for remedying this drawback includes supplementing the receiver with automatic gain control making it possible to adjust the amplitude of the signal received so as to allow good analog/digital conversion followed by correlation which will not be disturbed by waveforms of different amplitudes.